Control for room air conditioner with electric heat

ABSTRACT

A control system for regulating the energization of an electric heater used with an all season type room air conditioning unit. A rotary snap switch provides a multiple circuit arrangement having a common manual selector operating means which selects either an electric heating cycle with medium or high fan speed or a cooling cycle with low, medium or high fan speed. The switch provides for complete circuit isolation of the electric heater during the cooling phases to prevent possible current leakage to the air conditioning cabinet.

iitiited States Patent Ferdelman [451 May 30, 11972 CONTROL FOR ROOM AIR CONDITIONER WITH ELECTRIC HEAT [72] Inventor: Donald C. Ferdelman, Kettering, Ohio Primary Examiner-Charles Sikalo Attorney-William S. Pettigrew, Frederick M. Ritchie and Ed- 'ward P. Barthel ABSTRACT A control system for regulating the energization of an electric heater used with an all season type room air conditioning unit. A rotary snap switch provides a multiple circuit arrangement having a common manual selector operating means which selects either an electric heating cycle with medium or high fan speed or a cooling cycle with low, medium or high fan speed. The switch provides for complete circuit isolation of the electric heater during the cooling phases to prevent possible current leakage to the air conditioning cabinet.

'1 V v 2 Claims, 3 Drawing Figures Patented May 30, 1972 lat;

3 rld 8LAFRRYOL RCU FUNCTION mm 2?. POSITION A B C F D E 50 26 |o-| lO-2 ||-4 78 7-9 3-12 5-6 a? FULL ccw x x x x MED. HEAT cw 60' x x x x H! HEAT )2 '2; Z Z 23 cw I20 OFF cw I80 x x COOL cw 240' x x COOL CW X X L0 INVENTOR.

one/d CJemQ/mzn B Y ATTORNEY CONTROL FOR ROOM AIR CONDITIONER WITH ELECTRIC I-[IEAT This invention is directed to an improved control system for an all season air conditioner of the type using electric resistance heater means to heat the conditioned area.

In my U.S. Pat. No. 3,373,800, issued Mar. 19, 1968 and copending patent application Ser. No. 793,460 filed Jan. 23, 1969, and now U.S. Pat. No. 3,532,509 granted Nov. 3, 1970 there are disclosed reverse cycle or heat pump air conditioning units having controls for an auxiliary electric heater to provide heat when reverse cycle refrigeration is not efficient. The present invention concerns a control system for an air conditioner which employs an electric heater as the sole heating means to effect transfer of heat to the conditioned area.

It is therefore an object of this invention to provide an improved control system for an air conditioner providing electric heater means as the sole means to supply heat to the conditioned area.

It is a further object of the present invention to provide a control system for such an air conditioner that will electrically isolate a single coil resistance heater to insure against leakage current through the heater circuit during the cooling operatron.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the Drawings:

FIG. 1 is 'a wiring diagram illustrating my control system for an all season air conditioning unit embodying one form of my invention;

FIG. 2 is a chart showing the closed positions of the selector switch as on to perform the desired functions; and

FIG. 3 is a diagrammatic view of an all season air conditioning system to which the control system is applied.

Referring now to the drawing and more particularly to FIG. 3, there is shown diagrammatically an all season air conditioning system including a motor compressor unit having its outlet 22 connected to the outdoor heat exchange coil 24 which transfers heat from a suitable compressed refrigerant to the outdoor air. This transfer is greatly increased by the outdoor air fan 26 which is operated by a fan motor 28. The circulation of the outdoor air in heat transfer with the outdoor coil 24 causes the condensation of the compressed refrigerant which is forwarded through line 30 to conventional restrictor means 32 for expansion and thence through line 34 to the indoor heat transfer cooling or evaporator coil 36 where the refrigerant evaporates and absorbs heat from the air in the room to be cooled. This absorption of heat is increased by the indoor centrifugal cooling fan 38 which also is driven by the fan motor 28 and which circulates air from the conditioned area or room in heat transfer with the indoor cooling or evaporator coil 36.

The evaporated refrigerant returns from the coil 36 through line 40 to the compressor 20. An electrical resistance heater assembly is provided to furnish heat which comprises a single resistance element heater 42 disposed in duct 43 in the air conditioner of FIG. 3 spaced between the cooling coil 36 and the cooling fan 38. The electric resistance element heater 42, which in the preferred form is a single heater coil disposed in a rectangular frame support (not shown) and supported thereby in the form of a continuous elongated heater coil of resistance wire which extends back and forth between the support in zigzag fashion. The heater wire is 18 gauge-cold resistance 14.6 ohms having a rating of 3,400 watts at 230 volts suitable for operation at temperatures up to 2,100 F. When the heater 42 is energized it heats the air circulated through the cooling coil 36 by the cooling fan 38. It is important to note that in smaller size air conditioning units, having capacities of the range of 9,000 to 12,000 BTU/Hm, the lateral space provided between the cooling coil 36 and the fan 38 in the duct 43 is limited to the extent that it is not possible to provide two banks" or sets of heater coils or two heater rows in parallel without modifying the unit to increase the overall depth of the unit. Applicants control system allows the use of a single heating element or coil to provide two levels of heat output in a manner that will be explained below.

In FIG. l, the supply conductor L connects to movable switch blades A and B of a multiple selector six position manual rotary control or snap switch through the conductor 10 connected from the terminal block 50, while the rotary switch blade C is connected to the terminal block 50 through the conductor 1 1. It will be seen that conductor ll connects the sixth fixed contact of the switch blade A below a series of five dead contacts with the low speed winding 52 and the conductor 2 connects the first and fifth contacts to the junction of the low speed winding 52 and medium speed winding 53 of the fan motor 28. The conductor 4 has a branch 54 which connects the second and fourth fixed contacts of rotary switch blade C with the juncture of the medium speed winding 53 and main winding 55 and a second conductor 56, having fan capacitor 57, which connects to the phase winding 58 of the fan motor 28. The switch blade contacts A, B and C form first, second and third selective contact means of a first multiple selector switch means for controlling the operation of the fan motor 28.

The fan motor 28 may have any form of control desired to provide high, medium and low speed terminals. An internal motor protector 59 of the bimetal type connects the phase winding and main winding junction terminal 61 with a second terminal block 62 by means of conductor 63, which is connected to the other supply conductor L With this arrangement as seen in the chart of FIG. 2 low speed fan operation is provided in the lowest or (300) clockwise position of the selector switch, medium speed operation is provided in the first medium heat position (0 or full counter clockwise) and fifth medium cool position (250) while high speed operation is provided in the second high heat 60) and fourth high cool (180) positions, with the third position (120) having no connections for providing an OFF position.

When cooling is desired the selector switch is rotated to either the fourth, fifth or sixth positions such that the supply line L1 connects through conductors 66, 67 from the terminal block 50 to the movable double-throw switch members 68 and 69 respectively of the stage type thermostat 70 which is responsive to room air temperature. The switch member 68 is of the snap-action type and at higher room temperatures of the thermostat 70, such as, for example 76 F., this switch member 68 will be moved into engagement with an upper contact 71 which is connected by a conductor 72 to an overload bimetal thermostat 73 which is in turn connected by conductor 74 to the main winding 79 and phase winding 80 of compressor motor 20. The conductor 8 connects the opposite side of the compressor motor main winding 79 and running capacitor 81 to the fourth, fifth and sixth contacts of a movable switch blade F which in turn is connected by conductor 7 to terminal block 62 and thence to supply conductor L to complete the cooling circuit. The movable blade contact F together with movable blade contact G form first and second selective contact means of a third multiple selector switch means operative in both the cooling and heating phases of operation of the air conditioner system.

When heating is desired the operator simply turns the selector switch to either the first or second position. Thus, when the room temperature is lowered, for example to 72 F the lost motion connection of the stage thermostat 70 will move the double throw switch member 68 into engagement with its lower contact 76 which connects through the conductor 12 to the movable contact blade D of the selector switch. The switch blade D has its upper first and second contacts connected by the conductor 3 to the cathode of a diode rectifier 78 which has its anode in turn connected to a lead of the electrical heater 42. A fuse 83 is inserted in the circuit between the heater 42 and an overload bimetallic thermostat 82 such that a conductor 9 is connected to the first and second contacts of the movable contact blade G whereby conductor 7 leads to terminal block 62 and thence to supply conductor L2 to complete the heating circuit. It will be noted that the anode of the diode 78 is also connected by conductor 5 to first and second fixed contacts of the movable switch blade E while the conductor 6 is connected to the fixed contact 84 of the secondary single throw switch 69 of the thermostat 70. The movable switch blades D and E form first and second selective contact means of a second multiple selector switch means.

The stage type thermostat 70 operates in the following manner. If it should be set at 70 F as long as the temperature remains above 70 the conductor 72 will be connected to the compressor motor 20. If the temperature falls below 70 F., the double throw switch 68 will move downwardly into engagement with the stationary contact 76 connecting through the conductor 12 to the heating switch blade D. The conductor 3 allows current to flow through the diode to the heater 42. The rectifying action of the diode connected through conductor 3 to heater 42 conducts only during one-half the normal cycle resulting in approximately one-half of the maximum wattage output if the diode rectifier were not in the circuit. In the disclosed form the heater 42 is rated at 1,700 watts at 230 V.A.C. of low heat when energized by the circuit 3-12 through the diode 78. It should be noted that the diode 78 could be connected with reverse polarity, that is with its anode connected to conductor 3 and its cathode connected to a lead of the heater 42, without changing the heat output of the heater 42.

If the room temperature falls further, for example to 68 F., then the secondary stationary switch 69 will be moved downwardly to engage the stationary contact 84 which connects the conductor 6 to the movable switch blade E connecting with the heater 42 with the full current flow through conductor 5. In this high heat position the electric heater 42 is rated at 3,400 watts 230 V.A.C.

The rotary snap action selector switch, preferably manufactured by the General Electric Company under the designation, Series 255-Rotary switch, is controlled by a common operating shaft and cam which moves all of the seven movable contact blades A through G. The rotatable cam in the first or full counter clockwise position closes the circuits 10-2, 7-9, 3-12 and 5-6, as shown in the chart of FIG. 2, such that the cooling fan motor 28 is energized to run at medium speed while the heater 42 is supplied either one-half or full current flow by means of the two stage thermostat 70 and blades D and E through the diode circuit 78 or conductor 5, respectively. When the rotary switch is positioned at the second or counter clockwise position of 60 the circuits 11-4, 7-9, 3-12 and 5-6 are closed whereby the fan motor 28 is energized to run at full speed, while the heater 42 is again automatically adjusted by thermostat 70 for either low or high wattage output.

As stated above the movable switch blades F and G form first and second selective contact means of a third multiple selector switch means such that blade G is operative in the control circuit to electrically remove one side of the heater 42 from the supply conductor L2 during the cooling operation of the air conditioner. The switch blades D and E of the second multiple selector switch means are operative to electrically remove the other side of the heater element 42 from the supply conductor L1 during the cooling phase thereby electrically isolating the heater 42 in switch positions 3 through 6 to insure against excessive leakage current through the heater circuit to the air conditioner cabinet in the moist atmosphere during cooling operation.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is understood that other forms might be adopted.

What is claimed is:

1. A control system for a room air conditioning unit operable to selectively heat or cool air, the combination of a motor compressor unit, a condenser, an evaporator, and a restrictor member coupled between said evaporator and condenser, a cooling fan for blowing air to be cooled over said evaporator, a multiple speed motor driving said fan having low and medium and high speed terminals, an electric resistance heater disposed in a vertically extending space between said fan and said evaporator providing the sole means for heating the circulating air, and a circuit means for controlling the operation of said motor compressor unit and said electric heater, said circuit comprising first and second supply conductors for connecting said motor compressor unit and said electric heater to an alternating current power source, a six position manual rotary control including first, second and third multiple selector switch means, said first multiple selector switch means connected to said first supply conductor having a first selective contact means individually connected to said low speed terminal and having a second selective contact means individually connected to said medium speed terminal and having a third selective contact means individually connecting to said high speed terminal of said fan motor, a stage type dual thermostatic switch having a double-throw switch member and a single-throw switch member, said thermostatic switch connected to said first supply conductor and having first and second double-throw terminals, said first double-throw terminal connecting to a terminal of said motor compressor unit, said second double-throw terminal connecting to first selective contact means of said second multiple selector switch means, said second single-throw switch of said thermostatic switch means having its one single-throw terminal connected to second selective contact means of said second multiple selector switch means, an electric resistance heater having first and second terminals, a semiconductor diode rectifier electrically connected between said electric heater first terminal and said first selective contact means of said second multiple selector switch means, said second selective contact means of said second multiple selector switch means electrically connected directly to said electric heater first terminal, first selective contact means of said third multiple selector switch means electrically connected to a terminal of said motor compressor unit, second selective contact means of said third multiple selector switch means electrically connected to said electric heater second terminal thereby allowing said thermostatic switch to automatically energize said electric heater to supply either maximum wattage output or approximately one-half wattage output dependent upon whether said electric heater is switched into the circuit by said manual rotary control, said third multiple selector switch means connected to said second supply conductor whereby said manual rotary control being operative my means of said second and third multiple selector switch means to electrically isolate said electric heater during the cooling operation of said air conditioning system.

2. The air conditioning system as defined in claim 1 wherein said vertically extending space being limited by the proximity of said cooling fan and said evaporator, said electric heater comprising a single coil arranged in zigzag fashion in a vertical plane for location in said vertically extending space such that the single coil electric heater provides either the maximum wattage output or the approximately one-half wattage output.

Patent No. 3 66 OQ2 Dated may 3:9 1972 Inventon's) Donalfi 3 Ferdelman It is certified that error appears. in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Em. Column 1, line 8 the patent member "3532 509" ehoulfi reed 3;,537 5fl9 e Golumn 3 line 36 255" eheulci reao'i 225 n,

Signed and sealed this 29th day of May 1973,,

(SEAL) Attesc:

EDWARD MEFLETCHER JRQ ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. A control system for a room air conditioning unit operable to selectively heat or cool air, the combination of a motor compressor unit, a condenser, an evaporator, and a restrictor member coupled between said evaporator and condenser, a cooling fan for blowing air to be cooled over said evaporator, a multiple speed motor driving said fan having low and medium and high speed terminals, an electric resistance heater disposed in a vertically extending space between said fan and said evaporator providing the sole means for heating the circulating air, and a circuit means for controlling the operation of said motor compressor unit and said electric heater, said circuit comprising first and second supply conductors for connecting said motor compressor unit and said electric heater to an alternating current power source, a six position manual rotary control including first, second and third multiple selector switch means, said first multiple selector switch means connected to said first supply conductor having a first selective contact means individually connected to said low speed terminal and having a second selective contact means individually connected to said medium speed terminal and having a third selective contact means individually connecting to said high speed terminal of said fan motor, a stage type dual thermostatic switch having a doublethrow switch member and a single-throw switch member, said thermostatic switch connected to said first supply conductor and having first and second double-throw terminals, said first double-throw terminal connecting to a terminal of said motor compressor unit, said second double-throw terminal connecting to first selective contact means of said second multiple selector switch means, said second single-throw switch of said thermostatic switch means having its one single-throw terminal connected to second selective contact means of said second multiple selector switch means, an electric resistance heater having first and second terminals, a semiconductor diode rectifier electrically connected between said electric heater first terminal and said first selective contact means of said second multiple selector switch means, said second selective contact means of said second multiple selector switch means electrically connected directly to said electric heater first terminal, first selective contact means of said third multiple selector switcH means electrically connected to a terminal of said motor compressor unit, second selective contact means of said third multiple selector switch means electrically connected to said electric heater second terminal thereby allowing said thermostatic switch to automatically energize said electric heater to supply either maximum wattage output or approximately one-half wattage output dependent upon whether said electric heater is switched into the circuit by said manual rotary control, said third multiple selector switch means connected to said second supply conductor whereby said manual rotary control being operative my means of said second and third multiple selector switch means to electrically isolate said electric heater during the cooling operation of said air conditioning system.
 2. The air conditioning system as defined in claim 1 wherein said vertically extending space being limited by the proximity of said cooling fan and said evaporator, said electric heater comprising a single coil arranged in zigzag fashion in a vertical plane for location in said vertically extending space such that the single coil electric heater provides either the maximum wattage output or the approximately one-half wattage output. 